Chemically bonded ceramic radiation shielding material and method of preparation

ABSTRACT

A composition of matter and method of forming a radiation shielding member at ambient temperatures in which the composition of matter includes a ‘cold-fired’ chemically bonded oxide-phosphate ceramic cement matrix; with one or more suitably prepared and distributed radiation shielding materials dispersed in the ‘cold-fired’ chemically bonded oxide-phosphate ceramic cement matrix.

CROSS-REFERENCES TO RELATED APPLICATIONS

Notice: More than one reissue application has been filed for the reissueof U.S. Pat. No. 8,440,108. This application is an application forreissue of U.S. Pat. No. 8,440,108, which issued from U.S. patentapplication Ser. No. 12/133,209, filed Jun. 4, 2008; and is acontinuation application of U.S. Pat. No. RE46,797, which issued fromU.S. patent application Ser. No. 14/712,853, filed May 14, 2015, whichis an application for reissue of U.S. Pat. No. 8,440,108, issued May 14,2013, which is a continuation-in-part application of PCTapplicationInternational Application No. PCT/US2006/046722, filed Dec.6, 2006, now abandoned, which is a continuation of U.S. patentapplication Ser. No. 11/441,833 filed May 26, 2006, now abandoned, whichis a continuation-in-part application of U.S. patent application Ser.No. 11/295,708, filed Dec. 6, 2005, now abandoned.

BACKGROUND

1. Technical Field

The present invention relates to the field of chemically bondedoxide-phosphate ceramic and, more particularly, to chemically bondedoxide-phosphate ceramic having unique radiation shieldingcharacteristics.

2. Description of the Related Art

Radiation containment, encapsulation, and shielding, includingelectromagnetic, and microwave shielding, is of increasing andconsiderable importance in a technologically advanced society. Whilenuclear power generation offers an alternative to fossil fuel energysources, containment of waste materials currently raise the expense,thereby decreasing the overall economic feasibility of generating power.Other low level radioactive materials, such as medical wastes,industrial wastes, wastes from depleted uranium ordinance, and the like,also experience the same storage, shielding, and containment issues.Additionally, the proliferation of electronic devices has increased theneed to provide effective electromagnetic-shielding. Electronic devicessuch as cellular telephones, microwave ovens, and the like may requireelectromagnetic energy shielding that blocks radiated energy from beingdirected towards the user.

The medical diagnostic field also makes extensive use of radioactivematerials to aid in detection of human maladies. The utilization ofx-rays and other forms of radioactive material to detect these problemshas provided doctors with valuable insight into the patients medicalcondition. Drawbacks to these diagnostic methods include the shieldingnecessary to protect the patient and medical personnel from unwantedexposure to radiation and other forms of electromagnetic energy.Currently radioactive medical diagnostics make extensive use of lead asa shielding material. For example, a patient may wear a lead-lined vestto minimize exposure during an x-ray. Lead-lined drywall board isextensively used to provide shielding from primary and secondaryx-radiation caused by the primary x-ray beam as well as scattering ofthe primary x-ray beam during medical x-rays. The x-ray machine itselfmay require significant shielding, such as provided by lead sheeting, toprevent undue human exposure to radioactive materials.

Metallic lead shielding is extensively utilized because it allows forefficient shielding without unduly consuming space. For example, a sheetof lead less than one inch thick may be implemented to shield an x-raymachine.

Lead shielding drawbacks include the mass of lead, the difficulty informing structures for holding the lead sheeting in place, the desirefor aesthetically pleasing structures, as well as the well-documentedcarcinogenic human health hazards in the exposure to and handling oflead, and the like. Existing lead-lined bonded gypsum wallboard is verylabor intensive to properly install as a secondary and primary x-raybarriers in medical and dental x-ray rooms and facilities.

Other radiation shielding needs include the manufacture of non-leadwallboards that can effectively replace the existing industry standardlead-lined bonded gypsum wallboard used in medical and dental x-rayrooms and similar facilities worldwide. Space stations, satellites, andspacecraft are other areas of possible use for the present invention, asthe forms of available radiation shielding materials such as aluminumfoil and sheeting, lead dependent materials, and other proposedradiation shielding methods are known to either be minimally effective,require prohibitive thickness contributing to weight problems, sometimestoxic in nature, and often cumbersome relative to the need to developversatile, strong, durable, relatively easily repaired, compositeradiation shielding materials that provide uniquely reliable protectiveshielding in a space environment.

Utilization of cementious materials to contain and shield radioactivematerials, which is described in U.S. Pat. No. 6,565,647, entitled:Cementitious Shotcrete Composition, which is hereby incorporated byreference in its entirety, may be problematic as Portlandcement/concrete based systems implement weak hydrogen bonding (incomparison to ionic bonding and covalent bonding). Also these Portlandcement based systems suffer from high levels of porosity (in comparisonto other matrices, such as a polymeric based material and chemicallybonded oxide-phosphate ceramics), corrosion and cracking issues.

Portland cement matrices also require extensive curing (twenty-one days)to ensure proper matrix formation. Other alternatives such as apolymeric based matrix may offer lower porosity but may degrade whenexposed to organic solvents and either high or low pH materials.Portland cement matrices also are susceptible to corrosive attack from avariety of materials typically found in radioactive wastes.

Cold-fired ceramic cement materials, such as described in U.S. Pat. No.5,830,815, entitled: Method of Waste Stabilization via Chemically BondedPhosphate ceramics, U.S. Pat. No. 6,204,214, entitled:Pumpable/injectable phosphate-bonded ceramics, U.S. Pat. No. 6,518,212,entitled: Chemically bonded phospho-silicate ceramics, and U.S. Pat. No.6,787,495, entitled: Multi-purpose Refractory Material, all of which arehereby incorporated by reference in their entirety, do not disclose orsuggest incorporating radiopac composite admixtures and therefore do notprovide radiation shielding qualities. In an exemplary embodiment of the'815 patent, the following magnesium oxide-phosphoric acid reaction isshown as typical:MgO+H₃PO₄+H₂O→MgHPO₄.3H₂O

The '815 patent contemplates other metal oxides, including aluminumoxides, iron oxides, and calcium oxides, barium oxides, bismuth oxides,gadolinium oxides, zirconium oxides and tungsten oxides Minimizing thepH of the reaction, in comparison to a phosphoric acid (i.e., a morebasic reaction) is achieved through utilization of a carbonate,bicarbonate, or hydroxide of a monovalent metal reacting with thephosphoric acid prior to reacting with the metal oxide or metalhydroxide. Other contemplated metals (M′) being potassium, sodium,tungsten, and lithium. A partial exemplary reaction described in the'815 patent is:H₃PO₄+M₂CO₃+M′Oxide→M′HPO₄

Additionally the utilization of a dihydrogen phosphate to form theceramic at higher pH (in comparison to the utilization of phosphoricacid) was also indicated in the following reaction:MgO+LiH₂PO₄+nH₂O→MgLiPO_(4.()n+1)H₂O

Fired or low and high temperature curing ceramic materials as describedin U.S. Patent Application Publication No. 20060066013 entitled: LowTemperature Process For Making Radiopac Materials UtilizingIndustrial/Agricultural Waste As Raw Materials (such as over severalhundred degrees Celsius) do not offer a viable alternative to cold-firedoxide-phosphate bonded ceramic structures. High curing temperatures mayprevent the materials from being utilized in waste containment andshielding applications as high temperature firing (above several hundreddegrees Celsius) requires the components be formed and fired in a remotelocation prior to transport and assembly in the desired location. Hightemperature cured ceramics may not be practical for forming largecomponents due to the firing requirements. In-situ formation of firedceramics for waste containment may be problematic because of the wastesbeing contained and the location of final storage. Ammonia may beliberated during the firing process. Inclusion of ammonia in the ceramicmatrix may be detrimental to the resultant formation.

In U.S. Patent Application Publication 2002/0165082, entitled: RadiationShielding Phosphate Bonded Ceramics Using Enriched Isotopic BoronCompounds, which is hereby incorporated by reference in its entirety,the utilization of enriched boron compound additives in a liquorsolution for phosphate-bonded ceramics so as to provide radiationshielding is described. This document does not suggestradiation-shielding and encapsulation by combining ‘cold-fired’chemically bonded oxide-phosphate cementitious materials with radiopacfillers and admixtures such as barium sulfate, barium oxide andcompounds, gadolinium oxide and compounds, and cerium oxide and ceriumcompounds, tungsten oxides and compounds, and depleted uranium oxide andcompounds.

U.S. Patent Application Publication 20050258405 entitled: CompositeMaterials and Technologies for Neutron and Gamma Radiation Shielding,which is hereby incorporated by reference in its entirety, describes theuse of various radiopac composite material admixtures that are in someapplications bonded by various modified Portland cements, groutingmaterials, epoxies, and magnesium oxychloride/phosphate cement. It isimportant to note while magnesium oxychloride/phosphate is a similarsounding and written description of a cementitious bonding technique, itis in fact a distinctly different cementitious bonding technique, andone that is known to produce a more porous and less advantageous resultto the embodiments disclosed herein below regarding magnesiumoxide-monopotassium phosphate cementitious bonding qualities. Thispublished patent application neither includes nor recognizes thepotential superior qualities and benefits of chemically bondedoxide-phosphate cementitious techniques for the creation of usefulcomposite material radiation shielding.

BRIEF SUMMARY

Accordingly, the embodiments of the ceramic material and methoddisclosed and described herein provide ‘cold-fired’ chemically bondedoxide-phosphate ceramic cement or ceramic concrete composite materialswith unique radiation shielding qualities and characteristics for thecontainment, encapsulation, and shielding of radioactive materials,electromagnetic, and microwave energy. In addition, the disclosedembodiments incorporate unique radiation shielding qualities for ceramiccement or ceramic concrete building materials and constructionapplications, including the coating of existing contaminated Portlandcement and other cementitious and epoxy building and constructionmaterials that are or may become contaminated with harmful radioactiveand other harmful hazardous waste substances.

While a representative embodiment is described in the context of, but isnot limited to, attenuating x-radiation generated by X-ray machines anddevices in hospitals, medical and dental rooms and facilities, it can beincorporated into a number of products and permutations of products toaccomplish the attenuation of X-rays, including, but not limited to,wallboard for medical and dental rooms, including vertical walls,flooring, and ceiling applications, removable and permanent shieldingfor medical transport carts, grout joint compound for sealing anyleakage of x-radiation between two adjoining materials, and any otherapplication where the attenuation and blocking of x-radiation and othercontaminants is desired. While not experiencing the foregoing drawbacksof prior designs, oxide-phosphate ceramic cement structures formsignificantly lower porosity structures in comparison to Portland cementstructures.

In an aspect of one embodiment, a composition of matter and method offorming a radiation shielding member at ambient temperatures in whichthe composition of matter includes a ‘cold-fired’ chemically bondedoxide-phosphate ceramic matrix, and a radiation shielding materialdispersed in the ‘cold-fired’ chemically bonded oxide-phosphate ceramicmatrix, is disclosed.

Low level radiation shielding in the present invention employs variouscombinations of effective radiopac fillers such as powdered bariumoxide, barium sulfate, and other barium compounds, cerium oxide andcerium compounds, as well as powdered bismuth oxide and bismuthcompounds, gadolinium oxide and gadolinium compounds, tungsten oxide andtungsten compounds , depleted uranium and depleted uranium compounds,which are bonded together in an acid-phosphate solution comprised ofspecific proportions of magnesium oxide (MgO) powder and potassiumdihydrogen phosphate (KH₂PO₄) and water. The resultant compositechemically bonded oxide-phosphate ceramic materials have been shown toeffectively block medical x-rays by providing the necessary radiationshielding needed to attenuate x-radiation up to 120 kVp at a materialthickness up to 0.5 inches. Simply increasing the thickness of thesechemically bonded oxide-phosphate ceramic composite radiation shieldingmaterials effectively attenuates higher kVp energy levels.

In accordance with one embodiment, a composition of matter is providedthat includes a chemically bonded oxide-phosphate based ceramic matrixand a radiation shielding material, wherein the radiation shieldingmaterial is dispersed in the chemically bonded oxide-phosphate basedceramic matrix, and the radiation shielding material is selected fromthe group consisting of barite, barium sulfate, cerium oxide, tungstenoxide, gadolinium oxide, annealed leaded glass 40% to 75% both powderedand fibers, zeolites, clinoptilotites, celestites and depleted uranium.

In accordance with another aspect of the invention, the zeolite is madeup of the following components and the following approximate percentagesby weight, 52.4% SiO2, 13.13% Al203, 8.94% Fe203, 6.81% CaO, 2.64% Na2O,4.26% MgO, and MnO 10%.

In accordance with another aspect of the invention, barite by weight isapproximately in the range of 89% to 99% BaSO₄ and in the range of 1% to5.8% silicates, and wherein the range of percentages by weight ofzeolite that will be present in the composition of matter of claim 2 is0.2% to 50%.

In accordance with another aspect of the invention, the phosphate basedceramic matrix is selected from the group consisting of KH₂PO₄(potassium dihydrogen phosphate), MgHPO₄ (magnesium hydrogen phosphate),Fe₃(PO₄)₂ (iron (II) phosphate), Fe₃(PO₄)₂8H₂O(iron(II) phosphateoctahydrate),FePO₄ (iron(III) phosphate), FePO_(4.)2H₂O (iron(III)phosphate dihydrate), AlPO₄ aluminum phosphate, AlPO_(4.)1.5H₂O(aluminum phosphate hydrate), CaHPO₄ (calcium hydrogen phosphate),CaHPO_(4.)2H₂O (calcium hydrogen phosphate dihydrate), BiPO₄ (bismuthphosphate), CePO₄ (cerium(III) phosphate), CePO_(4.)2H₂O (cerium(III)phosphate dihydrate), GdPO_(4.)1H₂O (gadolinium phosphate),BaHPO₄(barium hydrogen phosphate), and UPO₄ (depleted uranium (U-238)phosphate).

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory onlyand are not restrictive of the embodiments as claimed.

DETAILED DESCRIPTION

Reference will now be made in detail to the presently preferredembodiments of the invention. The present invention is directed to acomposition of matter and method for forming a radiation-shieldingmember at ambient conditions. Those of skill in the art will appreciatethe composition of matter of the present invention is intended to beutilized for shielding and attenuation of various forms of radiation,including x-radiation, the electromagnetic and microwave spectrums; andenergy from electron-beam welding (bremsstrahlung radiation or secondaryradiation), and the like.

The composition of matter and method provides an efficient compositionfor utilization in constructing members that exhibit radiation-shieldingcapability in a region of the electromagnetic spectrum. The resultantmaterial may be formed at ambient conditions in a rapid time frame(one-half hour curing to two days curing). This allows for the formationof a chemically bonded oxide-phosphate ceramic matrix with radiation,electromagnetic, and microwave shielding inclusion materials without thehigh temperature firing typically required. Typical high temperaturefiring may exceed several hundred degrees Celsius and usually may occurin the range about 1800° C. (one thousand eight hundred degreesCelsius). While the present method of ‘cold-firing’ (curing at ambienttemperatures) may occur at or below 100° C. (one hundred degreesCelsius), the foregoing may allow for in-situ formation of a member suchas a shielding structure or efficient transportation and installation ofa preformed panel or structure formed of the composition of matter incomparison to other radiation shielding materials. For example, astructure formed in accordance with the present invention may allow fora fully cured wall partition to be formed and ready for use in the timeframe of several days. A composition of matter of the present inventionimplements a ‘cold-fired’ chemically bonded oxide-phosphate ceramicmaterial so as to form a matrix for including additional radiationshielding material therein. A chemically bonded oxide-phosphate ceramicmatrix may be formed by the incorporation of a metal oxide with aphosphate containing substance or material. Those of skill in the artwill appreciate that the resultant chemically bonded oxide-phosphateceramic may be a hydrated form based on the constituent metal phosphate.Suitable metal oxides may include metal oxides in which the cationiccomponent is associated with radiation shielding, such that theresultant metal phosphate ceramic may exhibit radiation-shieldingcapability. Suitable phosphates containing substances or materialsinclude potassium dihydrogen phosphates, phosphoric acid, an acidphosphate, monohydrogen phosphates, and the like. Suitable oxidesinclude magnesium, iron (II or III), aluminum, barium, bismuth, cerium(III or IV), gadolinium, tungsten, and depleted uranium (III)(substantially uranium 238).

The resultant chemically bonded oxide-phosphate ceramics may includeKH₂PO₄ (potassium dihydrogen phosphate), MgHPO₄.3H₂O (magnesium hydrogenphosphate trihydrate), MgHPO₄ (magnesium hydrogen phosphate),Fe₃(PO₄)₂(iron(II) phosphate), Fe₃(PO₄)_(2.)8H₂O(iron(II) phosphate octahydrate),FePO₄ (iron(III) phosphate), FePO_(4.)2H₂O (iron(III) phosphatedihydrate), AlPO₄ (aluminum phosphate), AlPO_(4.)1.5 H₂O (aluminumphosphate hydrate), CaHPO₄ (calcium hydrogen phosphate), CaHPO_(4.)2H₂O(calcium hydrogen phosphate dihydrate), BiPO₄ (bismuth phosphate), CePO₄(cerium(III) phosphate), CePO_(4.)2H₂O (cerium(III) phosphatedihydrate), BaHPO₄ (barium hydrogen phosphate) and UPO₄(depleted uranium(U-238) phosphate). In further instances, different metal and rare earthphosphates/hydrogen phosphates such GdPO₄1H₂O gadolinium phosphate maybe implemented as well. Suitable multiple metal phosphates may includemagnesium hydrogen phosphate, iron(III) phosphate, aluminum phosphate,calcium hydrogen phosphate, cerium(III) phosphate, and barium hydrogenphosphate. In an embodiment the ceramic matrix is of the formula:ceramic matrix is of the formula: MHPO_(4.xH2)O in which M is a divalentcation selected from the group consisting of: Mg (magnesium), Ca(calcium), Fe (iron(II)), and Ba (barium); wherein x is at least one of0 (zero), 2 (two), 3 (three), or 8 (eight).

In a further example, the chemically bonded oxide-phosphate basedceramic matrix is of the formula: MPO_(4.xH2)O in which M is a trivalentcation selected from: Al (aluminum), Ce (cerium (III)), U²³⁸ (depleteduranium); and Fe (iron(III)); and x is at least one of 0 (zero), 1.5(one point five), or 2 (two). In further embodiments, a multiple layerstructure is formed to provide effective attenuation across a range ofkilovolt-peak (kVp) ranges. For example, a multiple layer material isformed via a casting or spray application to form a mono structureexhibiting shielding and attenuation across a range. The layers may beformed of differing combinations of ceramics and shielding materials toachieve the desired shielding and attenuation. For example, a firstlayer is formed with a bismuth shielding material while a second layeris formed of a cerium based ceramic. A third layer of a ceramicincluding a barium sulfate shielding material may be included as well.In the present example, cerium oxide is included for its attenuationX-rays at 120 kVp at a material thickness of 0.5 inches. Greatermaterial thickness will effectively attenuate x-radiation at higherlevels of energy. Also, in one embodiment the bismuth can be prepared orapplied in a manner that shields radiation below gamma rays on theelectromagnetic spectrum in wavelength, frequency, or photon energy.

Thus, two or more radiation shielding materials can be employed toachieve a multiple layer structure. Because chemically bondedoxide-phosphate ceramic matrices successfully bond to themselves, use oftwo or more radiation shielding materials increases the range ofshielding through layering of the materials in the ceramic matrix.Layering in one embodiment is accomplished through separate curing ofindividual layers, and then the layers are bonded together in a knownmanner, such as forming subsequent layers on previously cured layers orby bonding previously cured layers using a oxide-phosphate bondedceramic adhesive.

In embodiments of the aforementioned layer process, suitable radiationshielding materials may be dispersed in the oxide-phosphate ceramiccement matrices. Those of skill in the art will appreciate thatcombinations of shielding materials may be incorporated into a singlematrix to provide attenuation across a portion of the electromagneticspectrum, such as X-rays, microwaves, and the like regions or portionsof regions of the electromagnetic spectrum. Examples include powders,aggregates, fibers, woven fibers and the like. Exemplary materialsinclude barite, barium sulfate, bismuth metal, tungsten metal, annealedleaded glass fibers and powders, cerium oxide, zeolite, clinoptilotite,plagioclase, pyroxene, olivine, celestite, gadolinium, suitable forms oflead, and depleted uranium.

A zeolite may be approximately by weight percentage 52.4% (fifty twopoint four percent) SiO₂ (silicon dioxide), 13.13% (thirteen point onethree percent) Al₂O₃ (alumina oxide), 8.94% (eight point nine fourpercent) Fe₂O₃ (ferric oxide), 6.81% (six point eight one percent) CaO(calcium oxide), 2.64% (two point six four percent) Na₂O (sodium oxide),4.26% (four point two six percent) MgO (magnesium oxide). While baritemay be approximately 89% (eighty nine percent) or above, BaSO₄ (bariumsulfate) and 5.8% (five point eight percent) silicates with theremainder consisting of naturally varying percentages of titaniumdioxide, calcium oxide, magnesium oxide, manganese oxide, and potassiumoxide. The foregoing approximation is dependent on naturally occurringweight percentage variations. In one embodiment, the zeolite componentof the ceramic is either a basalt zeolite or clinoptilolite of aparticle size in the range of from about 5 microns to about 500 microns(minus 30 to plus 325 mesh −25% passing 325 mesh). Research carried outhas shown the best results are obtained when zeolite is present in aweight range of about 2-20% by weight zeolite to ceramic. It has beenfound that with the combination of barite and zeolite, enhancedradiation protection is provided over what is provided by using baritealone, because of the isotope encapsulation abilities of zeolite.

The zeolite is preferably used in a natural form, although a syntheticzeolite can be used. As understood by those of skill in the art, themain zeolite formula is M2/nO.Al2O3.xSiO2.yH2O, with M defining thecompensating cation with valence n [7]. The structural component isMx/n[(AlO2)x(SiO2)y].zH2O, with the general structure as arrangements oftetrahedra in building units from ring structures to polyhedra.

In an exemplary embodiment, a method of constructing a shielding memberincludes mixing a metal oxide, such as a metal oxide including divalentmetal cation with a phosphate containing material. Suitable phosphatecontaining materials include phosphoric acid, hydrogen phosphatesubstances (such as monohydrogen phosphates and potassium dihydrogenphosphates) and the like. A radiation shielding material may beincorporated into the metal oxide and phosphate containing material mix.Incorporating may include dispersing aggregate, powder, and fibers.Woven fibers may be incorporated as part of a casting process, alayering process, or the like. The incorporated radiation shieldingmaterial and metal oxide-phosphate ceramic may be cured to hardness(maximum compressive strength) at ambient conditions. For example, themember may be cast in place and the curing reaction being conducted atambient conditions (i.e., ambient temperature). In an embodiment, thereaction and curing of the radiation shielding member occurs at, or atless than, 100° C. (one hundred degrees Celsius). Those of skill in theart will appreciate that the porosity of the resultant member may bevaried based on the reagents selected. Excellent admixture aggregates soas to significantly decrease porosity and add strength are fly ash,bottom ash, and wollastinite that can be added in ratios ranging from15:85 and 50:50, as well as other sparsely soluble silicates asexplained in U.S. Pat. No. 6,518,212, entitled: Chemically bondedphospho-silicat ceramics: A chemically bonded phospho-silicate ceramicformed by chemically reacting a monovalent alkali metal phosphate (orammonium hydrogen phosphate) and a sparsely soluble oxide, with asparsely soluble silicate in an aqueous solution. The monovalent alkalimetal phosphate (or ammonium hydrogen phosphate) and sparsely solubleoxide are both in powder form and combined in a stochiometric molarratio range of (0.5-1.5):1 to form a binder powder. Similarly, thesparsely soluble silicate is also in powder form and mixed with thebinder powder to form a mixture. Water is added to the mixture to form aslurry. The water comprises 50% by weight of the powder mixture in saidslurry. The slurry is allowed to harden. The resulting chemically bondedphospho-silicate ceramic exhibits high flexural strength, highcompression strength, low porosity and permeability to water, has adefinable and bio-compatible chemical composition, and is readily andeasily colored to almost any desired shade or hue. Other examples ofthese sparsely soluble silicates are Calcium silicate (CaSiO₃),Magnesium silicate (MgSiO₃), Barium silicate (BaSiO₃), Sodium silicate(NaSiO₃), Lithium silicate (LaSiO₃), and Serpentinite (Mg₆₄.O₁₀.{OH₈}).

In a specific embodiment, a radiation shielding member composed of acomposition of matter of the present invention is constructed by mixing1 lb. (one pound) of a metal oxide, monopotassium phosphate with 1 lb.(one pound) of radiation shielding material such as an aggregate,powder, or fiber filler attenuating material, and H₂O (water) is addedto approximately 20% (twenty percent) by weight, and the resultant‘cold-fired’ composite radiation shielding material is allowed to cure.In this embodiment, the metal oxide-to-monopotassium phosphate ratio, byweight, is 1/3 (one-third) metal oxide, such as dead-burned magnesiumoxide, to two thirds monopotassium phosphate, or MKP (KH₂PO₄) and afurther weight ratio of 15:85 to 50:50 of fly ash, bottom ash and othersuitable sparely soluble silicates. It should be noted that due to thediffering molar ratios between the ‘dead-burned’ magnesium oxide (MgO)and the monopotassium phosphate (MKP), and/or any suitable alternateoxides and phosphate materials employed, the aforementioned MgO, MKPweight/volume ratios may be varied and still produce effective bondingfor the intended attenuating/shielding admixtures.

In further embodiments, various carbonates, bicarbonate (such as sodiumbicarbonate, potassium bicarbonate and the like) or metal hydroxidesreagents may be reacted in a two step process with an acid phosphate tolimit the maximum reaction temperature of the metal oxide and the resultof the carbonate, bicarbonate or hydroxide reaction with an acidphosphate.

In further embodiments, other acids may be implemented to form aresultant metal oxide-phosphate ceramic-based material. The selection ofthe acid may be based on the metal oxide to be utilized; suitable metaloxides include divalent and trivalent metals (including transitionmetals and lanthanide series and actinide series metals). Other suitableacids include boric acid as a retardant (<1% of the total powder). Andin another embodiment hydrochloric acid is used as a catalyst whencertain oxide phosphate cementious blends such as a barium oxide, andbismuth phosphate blend are not suitably water-soluble.

In specific examples, mixing the selected ceramic matrix with thedesired shielding material formed exemplary compositions. In oneembodiment, the final combined mixture forms a product in which theshielding material is cemented or bonded with the ceramic matrix, whichincludes internal bonding or external bonding or both. In addition, theceramic matrix materials are in the range of −200 mesh or below. Thefollowing specific examples are only exemplary and utilized to explainthe principles of the present invention. The following procedures wereconducted in ambient conditions (e.g., temperature, pressure). Forinstances, carried out at a room temperature of between 65° F. to 85° F.(sixty-five degrees Fahrenheit to eighty-five degrees Fahrenheit) underatmospheric pressure. No attempt was made to fully homogenize thematerial to obtain uniform particles, while substantially uniformdistribution of shielding material within the ceramic matrix wasattempted.

For samples in which woven fiber shielding fabric material is utilized,the ceramic is hydrolyzed and cast in contact with the fabric material.In instances in which powdered shielding material are incorporated, theparticle size varied depending on the material. Ideally, the powderparticles are sized in the range of −200 mesh or below. Those of skillin the art will appreciate that a wide range of particle sizes may beutilized. Water is added to hydrolyze the dry mixture. The combinationof the water and ceramic oxide, phosphate and shielding material ismixed for a sufficient duration and with sufficient force to cause themixture to exhibit an exothermic rise of between 20%-40% (twenty percentto forty percent) of the original temperature of the mixture. Thehydrolyzed mixture was compacted via vacuum or vibratory or equivalentmethod to eliminate voids. Compaction is preferably conducted in acontainer, such as a polymeric container formed from polypropylene orpolyethylene, having a low coefficient of friction to facilitateremoval. The samples were allowed to harden to the touch (at leasttwenty-four hours) at ambient conditions.

The samples were submitted for x-ray lead equivalency testing. Thesamples submitted for testing were formed when a metal oxide such as MgO('dead-burned' Magnesium Oxide), a suitable sparsely soluble silicateand radiopac additives as set forth in the present disclosure, arestirred in an acid-phosphate solution, (such as monopotassium phosphateand water). The dissolution of the metal oxide forms cations that reactwith the phosphate anions to form a phosphate gel. This gel subsequentlycrystallizes and hardens into a coldfired ceramic. Dissolution of theoxide also raises the pH of the solution, with the cold-fired ceramicbeing formed at a near-neutral pH.

Controlling the solubility of the oxide in the acid-phosphate solutionproduces the chemically bonded oxide-phosphate ceramic. Oxides or oxideminerals of low solubility are the best candidates to form chemicallybonded phosphate ceramics because their solubility can be controlled.The metal oxide in the sample formulations is known as ‘dead-burned’Magnesium Oxide (MgO), calcined at 1300° C. or above in order to lowerthe solubility in the acid-phosphate solution. Oxide powders can bepretreated for better reactions with the acids. One technique includescalcining the powders to a typical temperature of between approximately1,200° C. and 1,500° C. and more typically 1,300° C. It has been foundthat the calcining process modifies the surface of oxide particles in amyriad of ways to facilitate ceramic formation. Calcining causesparticles to stick together and also form crystals; this leads to theslower reaction rates that foster ceramic formation. Fast reactions tendto form undesired powdery precipitates. Such ‘dead-burned’ magnesiumoxide can then be reacted at room temperature with any acid-phosphatesolution, such as ammonium or potassium dihydrogen phosphate, to form aceramic of the magnesium potassium phosphate. In the case of magnesiumoxide-mono potassium phosphate, a mixture of MgO ('dead-burned'Magnesium Oxide), KH₂PO₄ (Monopotassium Phosphate), and a suitablesparsely soluble silicate can simply be added to water and mixed from 5minutes to 25 minutes, depending on the batch size. MonopotassiumPhosphate dissolves in the water first and forms the acid-phosphatesolution in which the MgO dissolves. The resultant ‘cold-fired’,chemically-bonded oxide-phosphate ceramics are formed by stirring thepowder mixture of oxides and radiopac additives, including any desiredretardants such as boric acid as have been clearly described herein,into a water-activated acid-phosphate solution in which the‘dead-burned’ magnesium oxide (MgO) dissolves and reacts with themonopotassium phosphate (MKP) and in some applications a suitablesparsely soluble silicate such as wollastinite, and sets into a‘cold-fired’ ceramic cementious material.

TABLE 1 CERAMIC SAMPLE FORMULATION den- sity Sam- H20 ceramic shieldinglbs/ ple (g) (g) material (g) particle size ft² 1 112.0 198.0 462.0barium 10 μm (microns) 152.0 sulphate 2 112.0 220.0 220.0 barium 325mesh (bismuth) 197.0 sulphate 220.0 bismuth 3 112.0 198.0 462.0 bismuth325 mesh 225.0 4 112.0 198.0 462.0 cerium 5.24 μm (microns) 175.0 IIIoxide 5 112.0 264.0 264.0 barium 10 μm (microns)  74.0 sulphate 66.0bismuth 325 mesh (bismuth) 66.0 cerium III 5.24 μm (microns) oxide 6112.0 basalt powder 130.0 462

TABLE 2 CERAMIC SAMPLE ATTENUATION Sample Attenuation Designation 60 kVp80 kVp 100 kVp 120 kVp 1 99.99% 99.97% 99.76% 99.05% 2 99.99% 99.98%99.77% 99.64% 3 99.89% 99.85% 99.77% 99.70% 4 99.95% 99.92% 99.82%99.37% 5 99.96% 99.91% 99.66% 99.19% 6 89.17% 81.79% 75.36% 69.62% 797.34% 96.37% 93.81% 90.00% 8 56.08% 52.33% 47.83% 43.52% Measured Half3.0 mmA1 4.0 mmA1 5.1 mmA1 6.2 mmA1 Value Layer (HVL)

TABLE 3 CERAMIC SAMPLE LEAD EQUIVALENCY (MILLIMETERS PB) Sample LeadEquivalency (mm Pb) Designation 60 kVp 80 kVp 100 kVp 120 kVp 1 1.8* 1.800 1.535 1.065 2 1.8*  1.822 1.552 1.445 3 0.635 1.380 1.551 1.525 40.758 1.440 1.660 1.225 5 0.790 1.410 1.375 1.125 6 0.119 0.126 0.1300.129 7 0.242 0.390 0.428 0.362 8 0.064 0.068 0.070 0.070 Measured Half3.0 mmA1 4.0 mmA1 5.1 mmA1 6.2 mmA1 Value Layer (HVL) *Due to the highattenuation of this sample, lead equivalency cannot be accuratelyreported for a tube potential of 60 kVp. The lead equivalency will be noless than that of the next higher kVp setting. (Wherein kVp -kilovolt-peak; mmA1-)

It is understood that the specific order or hierarchy of steps in theprocesses disclosed is an example of exemplary approaches. Based upondesign preferences, it is understood that the specific order orhierarchy of steps in the processes may be rearranged while remainingwithin the scope of the present invention. The accompanying methodclaims present elements of the various steps in a sample order, and arenot meant to be limited to the specific order or hierarchy presented.

It is believed that the present invention and many of its attendantadvantages will be understood by the foregoing description. It is alsobelieved that it will be apparent that various changes may be made inthe form, construction and arrangement of the components thereof withoutdeparting from the scope and spirit of the invention, or withoutsacrificing all of its material advantages. The form herein beforedescribed being merely an explanatory embodiment thereof. An expectedspecific change is the eventual inclusion of nano-sized constituentmaterial preparation so as to increase the available surfaces principleof bonding. Most if not all of the chemically bonded oxide-phosphateradiation shielding ceramics described in the present patent can beproduced as cement, concrete, drywall material, coatings, and groutings,and can be poured, sprayed, troweled, and molded into a variety of formsand uses. Therefore it is the intention of the following claims toeventually encompass and include most, if not all, of these changes andpotentials.

In addition, the embodiments disclosed herein can be applied toradiation contaminated objects and structures, to encapsulate the sameand contain the contaminant within the object or structure, thusshielding and protecting objects external to the encapsulated object orstructure.

What is claimed is:
 1. A composition of matter comprising: a chemicallybonded oxide-phosphate based ceramic matrix; and a radiation shieldingmaterial, wherein the radiation shielding material is dispersed in thechemically bonded oxide-phosphate based ceramic matrix in an amount of40%-75% by weight and the radiation shielding material is selected fromthe group consisting of barium oxide, barium sulfate, cerium oxide,tungsten, tungsten oxide, gadolinium, gadolinium oxide, depleted uraniumoxide, wherein the oxide-phosphate based ceramic matrix is MgHPO4⋅3H2O(magnesium hydrogen phosphate trihydrate), or wherein theoxide-phosphate ceramic matrix includes at least two different metalphosphates.
 2. The composition of matter of claim 1 wherein the at leasttwo different metal phosphates are selected from the group consisting ofKH₂PO₄ (potassium dihydrogen phosphate), MgHPO₄ (magnesium hydrogenphosphate), Fe₃(PO₄)₂ (iron (II) phosphate), Fe₃(PO₄)_(2.)8H₂O (iron(II)phosphate octahydrate), FePO₄(iron(III) phosphate), FePO₄2H₂O (iron(III)phosphate dihydrate) AlPO₄aluminum phosphate, AlPO_(4.)1.5H₂O (aluminumphosphate hydrate), CaHPO₄(calcium hydrogen phosphate), CaHPO_(4.)2H₂O(calcium hydrogen phosphate dihydrate), BiPO₄(bismuth phosphate),CePO₄(cerium(III) phosphate), CePO_(4.)2H₂O cerium(III) phosphatedihydrate), GdPO_(4.H2)O (gadolinium phosphate hydrate), BaHPO₄(bariumhydrogen phosphate), and UPO₄ (depleted uranium (U-238) phosphate). 3.The composition of matter of claim 1 wherein the radiation shieldingmaterial is formed as at least one or more of the aggregates or powdersdispersed in the oxide-phosphate ceramic.
 4. The composition of matterof claim 1 wherein the at least two different metal phosphates areselected from the group consisting of magnesium hydrogen phosphate,iron(III) phosphate, aluminum phosphate, calcium hydrogen phosphate,bismuth phosphate, cerium(III) phosphate, gadolinium phosphate, andbarium hydrogen phosphate.
 5. The composition of claim 1, comprising atleast two radiation-shielding materials to form a multiple layerstructure, wherein the at least two radiation-shielding materials are inseparate layers of the multiple layer structure.
 6. A method ofconstructing chemically bonded oxide-phosphate based ceramic matrixradiation shielding at ambient temperature, comprising: providing amixture of (a) magnesium oxide, or at least two a metal oxides selectedfrom the group consisting aluminum oxide, magnesium oxide, iron(III)oxide; iron (II) oxide and calcium oxide; (b) a phosphate containingmaterial; (c) a radiation shielding material selected from the groupconsisting of barium oxide, barium sulfate, cerium oxide, tungstenoxide, tungsten, gadolinium oxide, gadolinium, depleted uranium oxide;and (d) a sparsely soluble silicate selected from the group consistingof calcium silicate (CaSiO₃), magnesium silicate (MgSiO₃), bariumsilicate (BaSiO₃), sodium silicate (NaSiO₃), lithium silicate (LaSiO₃),and serpentinite (Mg64.O10.{OH8}); adding an activator to the mixture;and allowing the mixture of the radiation shielding material, metaloxide, phosphate containing material in an amount of 40% -75% by weightand the sparsely soluble silicate to cure at ambient temperature.
 7. Themethod of constructing a radiation shielding member at temperatureconditions of claim 6 wherein curing occurs at less than 100° C. (onehundred degrees Celsius).
 8. The method of constructing aradiation-shielding member at ambient temperature of claim 6 wherein thephosphate containing material is phosphoric acid.
 9. The method of claim6 wherein the activator is water or an acid.
 10. A mixture comprising:magnesium oxide, or at least two metal oxides selected from the groupconsisting of magnesium oxide, iron (III) oxide; iron (II) oxide andcalcium oxide; a phosphate-containing material; a radiation shieldingmaterial selected from the group consisting of: barium oxide, bariumsulfate, cerium oxide, tungsten, tungsten oxide, gadolinium, gadoliniumoxide, and depleted uranium oxide; wherein the radiation shieldingmaterial is in an amount of 40%-75% by weight; and a sparsely solublesilicate selected from the group consisting of calcium silicate(CaSiO₃), magnesium silicate (MgSiO₃), barium silicate (BaSiO₃), sodiumsilicate (NaSiO₃), lithium silicate (LaSiO₃), and serpentinite(Mg₆₄.O₁₀.{OH₈}); wherein the composition forms a chemically bondedoxide phosphate ceramic matrix upon activation.
 11. The mixture of claim9 wherein the phosphate-containing material is potassium dihydrogenphosphates, phosphoric acid, or potassium monohydrogen phosphate. 12.The mixture of claim 9 wherein the metal oxide is magnesium oxide, andthe phosphate-containing material is potassium dihydrogen phosphate; andthe radiation shielding material is barium sulfate.
 13. The mixture ofclaim 9 wherein the metal oxide is magnesium oxide, and thephosphate-containing material is potassium dihydrogen phosphate; and theradiation shielding material is depleted uranium oxide.
 14. Aradiation-shielding composition, comprising: (1) a chemically bondedceramic matrix, comprising: a) magnesium phosphate; and b) wollastonite;and (2) a radiation-shielding material in an amount of 40% to 75%dispersed in the chemically bonded ceramic matrix.
 15. Theradiation-shielding composition of claim 14, wherein the magnesiumphosphate; is formed from MgO (magnesium oxide) and KH₂PO₄(monopotassium phosphate).
 16. The radiation-shielding composition ofclaim 15, wherein the MgO (magnesium oxide) is dead-burned magnesiumoxide.
 17. The radiation-shielding composition of claim 14, furthercomprising a powder or fibers dispersed in the chemically bonded ceramicmatrix.
 18. The radiation-shielding composition of claim 14, wherein themagnesium phosphate is MgHPO₄⋅3H₂O (magnesium hydrogen phosphatetrihydrate).
 19. The radiation-shielding composition of claim 14,wherein the radiation-shielding material is selected from the groupconsisting of barite, barium sulfate, powdered annealed leaded glass,fibers of annealed leaded glass, barium oxide, cerium oxide, tungsten ora tungsten-containing compound, tungsten oxide, gadolinium, gadoliniumoxide, depleted uranium oxide, iron oxide, bismuth or abismuth-containing compound, boron or a boron-containing compound,aluminum oxide, zeolites, clinoptilotites, celestites, depleted uranium,and combinations thereof.
 20. A radiation-shielding member comprisingthe radiation-shielding composition of claim
 14. 21. Theradiation-shielding member of claim 20, wherein the radiation-shieldingmember is configured for use as a radiation-shielding wall.
 22. Theradiation-shielding member of claim 20, wherein the radiation-shieldingmember is a single layer structure.
 23. The radiation-shielding memberof claim 20, wherein the radiation-shielding member comprises twolayers, each of the two layers having a different radiation-shieldingproperty.
 24. The radiation-shielding member of claim 23, wherein thetwo layers comprise different radiation-shielding materials.
 25. Amethod of constructing a radiation shielding member, comprising: (1)forming a mixture comprising: (a) MgO (magnesium oxide); (b) KH₂PO₄(monopotassium phosphate); (c) wollastonite; and (d) aradiation-shielding material in an amount of 40% to 75%; and (2) curingthe mixture to provide a chemically bonded ceramic matrix of MgHPO₄⋅3H₂O(magnesium hydrogen phosphate trihydrate) and wollastonite with theradiation-shielding material dispersed therein.
 26. The method of claim25, wherein the radiation-shielding material is selected from the groupconsisting of barite, barium sulfate, powdered annealed leaded glass,fibers of annealed leaded glass, barium oxide, cerium oxide, tungsten ora tungsten-containing compound, tungsten oxide, gadolinium, gadoliniumoxide, depleted uranium oxide, iron oxide, bismuth or abismuth-containing compound, boron or a boron-containing compound,aluminum oxide, zeolites, clinoptilotites, celestites, depleted uranium,and combinations thereof.
 27. The method of claim 25, wherein curingoccurs at less than 100° C.
 28. A method of shielding radiation emittingfrom a radiation source, comprising obstructing the radiation using aradiation shielding member according to claim 20.